Accurate Strong Gantry

[Ross77]

Normally if someone says that it cant be done then that is like a red rag to a bull and I try to come up with a solution, but now you have brought steel into the equation then I would agree with the others that it will be really difficult as the requirements are at opposite ends of the spectrum.

If it was Diy the you could compromise on the design and use the machine to the best of its abilities but you seem to be saying that it will be a commercial use so that wouldnt really be feasible.

If you did proceed you will need to two spindles.

1. Low speed with high ridigity and power at low speed for steel.
2. High speed and power at high speed for ali.

You would then need 10mm pitch ball screws on high power servo motors with high resolution encoders to get the accuracy. Etc etc.

It can be be done but like the others have said it will be expensive and you will still end up compromising the design. It may well be cheaper and better from a production point of view to build 2 specific machines. Good luck

[vargai]

It may well be cheaper and better from a production point of view to build 2 specific machines. Good luck

IMO you will be much better building a router that will cut everything in it's capabiltys, Ie woods,plastics etc to a high standard.
Then buy a milling machine at later date that will do and give the same high accurecy and repeatabilty with Aluminium and Steel etc.

Sorry for late answering. I could have placed this post to a general thread since by going through my one the searching on the good design led the doubt about the primary aim.
Reading the posts after my latest design I recognized or at least felt the generally weak points. Sorry for seeming stubborn. It is not meant to happen. My tenacity is all about my goals and not the way and method to reach it. It is not easy to abandon a main intent and to say right away yes, or no.
So thank you all who involved for your efforts and advice in highlighting my weakness.
I hope I do not have to turn my back on metal and will be able to build a good router for Al and other softer material.

[GEOFFREY]

Hi, I said that I would not post again on this topic, but your final sentence sounds very sensible. G.

[Ross77]

Hi Vargai
Don't be put off building a machine, maybe you should proceed and prove us all wrong :o)

everyone is just trying to help you get the best results.

[vargai]

Hi Vargai
Don't be put off building a machine, maybe you should proceed and prove us all wrong :o)
everyone is just trying to help you get the best results.

Of course I do not , because the goal is not to prove that is impossible but to build what is possible:)
Let me ask something I have a doubt about.
I saw your latest general frame design and I am wonder how the steel hollow tube beams bracing react to the machining force on a router .(generally).The seems like "strings" and source of resonance but I have never seen or heard router during operation.
Actually I am wonder of the smallest applicable size ie 50x50x3 showed many times.

[Ross77]

It was meant as more of an idea than a finished design. Yes if the bracing became long and slender then it could resonate. They are all different lengths so they would have different resonant frequencies.

It is also the base frame so the bolting down fixings will help with damping.

Like I said it was more of a basic idea, I did quite a few different options and it started getting messy. So look at the bracing for layout and size accordingly.

I plan to build a similar heavy duty fixed gantry mill, better not mention that I want it to cut steel. He he

[GEOFFREY]

I plan to build a similar heavy duty fixed gantry mill, better not mention that I want it to cut steel. He he

With a smallish (600x400?) working area and a strong solid fixed gantry machine, I do not see why steel should be
too much of a problem. My machine (converted commercial PCB drill/router) had a steel section right across the middle of the aluminium table that was used to locate dowelled stacked boards for drilling etc. Careless use by the previous owners operatives has led to to both the alluminium and steel parts of the bed covered in holes and grooves all over the place!!! These have maily been cut with sub 1mm cutters, which probably did end up breaking, but not before inflicting serious scars everywhere. With a slower speed spindle, and the right cutter I feel sure that I could cut steel, but would not need to be greedy with regards to feed speed DOC etc. G.

[vargai]

It was meant as more of an idea than a finished design.

It was not criticism just gathering data for a steel based light weight moving gantry DIY router that can be used in its scope and additionally I can check , try some solutions. I red about HSM spindle and HSM Al milling and aware of that this is also a wide spectrum so I will be happy with the result that a router can give.
Not forgetting the steel I am planning to attach an easy removable really small, geared spindle driven by the HS one with belt or directly coupled. (EDIT: i see now that the belt not good at this speed) In this method the supposed extension of the original spindle would be only about 60-80 mm and the force not bother the main spindle bearings
With 1:0,5 ratio (12000-to 6000 rpm) and quite enough torque I probably can make a typical steel milling with DIA 4-5 mm mill.
This would be making opening on a flat parts of electrical enclosures ( mainly doors) and mainly Dia 30,5 mm holes for push buttons.
The only problem is that the thickness is 2 mm but I suppose a 3kW spindle can do it with full DOC( the pre drilling- hydraulic method works but too slow and there are other shapes). This will not be bottleneck if I cannot do it just an idea.
pls adjust me if someone has experience.
One question about the steppers:
Normally they do their job and do not care of step loss and go on.
Is there any no too expensive mean, method to persuade them to stop at step loss and not multiply the mistake.
Thanks